Vehicles, such as automobiles, are generally mounted with seat belt devices that restrain an occupant in a seat that includes a seat portion on which the occupant sits and a backrest portion positioned back of the occupant. Such a seat belt device has webbing that restrains the occupant, a retractor that winds the webbing, a guide anchor that is provided on a vehicle body side and guides the webbing, a belt anchor that fixes the webbing to the vehicle body side, a buckle disposed on a side surface of the seat, and a tongue disposed to the webbing. The tongue is fitted into the buckle, thereby to restrain the occupant in the seat with the webbing.
The webbing in restraining the occupant can be classified into a lap belt that restrains the occupant's waist with the webbing between the belt anchor and the tongue, and a shoulder belt that obliquely restrains the occupant's shoulder with the webbing between the guide anchor and the tongue.
In such a seat belt device, it has been already proposed to arrange a pretensioner capable of retracting the lap belt of the webbing in the belt anchor, in order to improve performance of restraining the occupant in a vehicle collision.
Such a pretensioner includes, for example, as described in Japanese Unexamined Patent Application Laid-open No. 2009-173103, a wire connected to the lap belt, a piston disposed at an end of the wire, a cylinder that slidably accommodates the piston, a gas generator that applies driving force to the piston, and a housing that communicatively connects the cylinder and the gas generator. Additionally, the wire inserted into the housing is inserted into a protection-seal body, which is integrally formed by a protection member and a seal member, and the protection-seal body is fixed inside the housing by a retaining ring.